This invention relates to the construction of an automatic weighing apparatus of the type having a circular array of plural weighing mechanisms each of which comprises a load cell. More particularly, the invention relates to the construction of an automatic weighing apparatus in which the load cells can be inspected and repaired with facility.
Of the types of automatic weighing apparatus which are now available, some include a plurality of weighing mechanisms rather than just a single weighing mechanism. One example is referred to as a combination computing type automatic weighing apparatus which weighs out articles by selecting a combination of the weighing mechanisms that gives a total weight closest to a preset target weight, and then discharging the articles from the weighing hoppers corresponding to the selected weighing mechanisms, whereby the weight of the discharged articles will be closest to the target weight.
FIG. 1 is a top plan view illustrating such an automatic weighing apparatus, and FIG. 2 is a side view of the same. In this automatic weighing apparatus, a plurality of weighing hoppers 2 are mounted in a circular array above the circumference of the top opening of a collecting chute 1. Each weighing hopper 2 is operatively associated with a weighing mechanism 3 designed to weigh out articles contained in the weighing hopper 2. A distribution table 4 is supported on an electromagnetically operated vibrator 5 for supply troughs 6 and is set into helical reciprocating rotation. The supply troughs 6 are mounted radially on the outer periphery of the distribution table 4 and are vibrated by corresponding electromagnetic vibrators 7. Sensors 8 are used for optically sensing the quantity of the articles on the distribution table 4. A pool hopper 9 is provided between each weighing hopper 2 and the supply trough associated therewith. Each weighing hopper 2 and the pool hopper 9 associated therewith are provided with a drive unit 12 and levers 10, 11 adapted for opening and closing the hoppers 2, 9.
The computerized combinatorial weighing apparatus thus constructed operates as follows.
The articles are supplied from the distribution table 4 through supply troughs 6 into pool hoppers 9 and thence into weighing hoppers 2. The articles thus received in the weighing hoppers 2 are weighed by the weighing mechanisms 3 associated therewith. Based on the weights measured by the weighing mechanisms 3, a control unit, not shown, of the weighing apparatus performs a combinatorial weighing operation by comparing the result of each combinatorial adding operation performed on the article weights with a preset target weight and selecting the combination of articles, known as the best combination, that gives a total weight equal to the target weight or closest to the target weight. In this case, the number of articles in the combination may be arbitrary or predetermined, as desired. The control unit then operates to open the thus selected weighing hoppers 2 by the operation of the levers 10, 11 so that the articles giving said best combination are released into the collecting chute 1 from the weighing hoppers 2 to be discharged towards a packaging machine or a bucket conveyor, not shown. This will leave the selected weighing hoppers 2 empty. Articles are then newly delivered from the corresponding pool hoppers 9 into said weighing hoppers 2, leaving these pool hoppers 9 empty, whereupon a new supply of articles is delivered from the distribution table 4 and the corresponding supply troughs 6. The weighing operation can be continued in this manner by repeating the foregoing steps.
Each of the weighing mechanisms 3 in the above-described automatic weighing apparatus employ weighing means that rely upon compact, highly accurate load cells. Each load cell includes a strain gauge affixed to the upper and lower beams of a rectangular frame, and is adapted to weigh articles by relying upon a variation in the resistance of the strain gauge caused by a load applied to a load receiving member. With the conventional automatic weighing apparatus, the weighing mechanisms 3 are arrayed in radiating fashion so that the beams of the load cells lie along radial lines pointing to the center of the apparatus, as illustrated in FIG. 3 which is a simplified top view of the apparatus of FIG. 2 as it would appear if viewed along the line I--I with all but the weighing mechanisms 3 removed. As a result, a great amount of space is required for the installation of the weighing mechanisms, and both inspection and repair of the load cells are laborious tasks since the operator must perform the necessary work between adjacent ones of the weight mechanisms 3 where the available space is so small.